Generally, a secondary battery may be rechargeable and have increased capacity. A representative example of the secondary battery includes a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, and the like. Among them, the lithium ion battery has been spotlighted as the next generation power source due to excellent characteristics such as a long lifespan, high capacity, and the like. Among them, a lithium secondary battery, which has operating voltage of 3.6 V or more, is used as a power supply of a portable electronic device or several lithium secondary batteries are connected in series with each other to thereby be used for a high output hybrid vehicle. Since this lithium secondary battery has operating voltage three times higher than that of the nickel-cadmium battery or the nickel-metal hydride battery and is more excellent in view of energy density characteristics per unit weight than the nickel-cadmium battery or the nickel-metal hydride battery, the use of the lithium secondary battery has rapidly increased.
The lithium secondary battery may be manufactured in various types. A representative type of the lithium secondary battery may include a cylindrical type and a prismatic type that are mainly used for the lithium ion battery. A lithium polymer battery that has been recently spotlighted is manufactured in a pouch type having flexibility, such that it has a relatively free shape. In addition, the lithium polymer battery has excellent stability and light weight, such that it is advantageous for slimness and lightness of the portable electronic device.
FIG. 1 is a view showing a structure of a pouched cell of a secondary battery according to related art and FIG. 2 is a view showing a longitudinal cross-section of the pouched cell of the secondary battery according to the related art. As shown, the pouched cell 10 includes a battery part 11 and a case 12 including a battery part space 12b receiving the battery part 11. The battery part 11 has a shape in which a plurality of positive electrode plates 11a, separators 11b, and negative electrode plates 11c are stacked. The positive electrode plate 11a of the battery part 11 is electrically connected to a positive electrode tap 13 and the negative electrode plate 11c is electrically connected to a negative electrode tap 14.
In addition, the case 12 is a pouched type case having an intermediate layer formed of a metal foil, wherein the metal foil has an inner and outer cover layers attached to both surfaces thereof and made of an insulating film. Since the pouched type case has excellent formability, it may be freely bent. The case 12 is provided with the battery part space 12b capable of receiving the battery part 11 as described above and a closed surface 12a provided to a surface which is heat-sealed along an edge of the battery part space 12b. 
The pouched cell 10 having the configuration described above adheres the case 12 and the battery part 11 to each other by vacuum adsorption in a state in which the battery part 11 is received in the case 12 (see arrows). However, since each of the positive electrode plate 11a, the separator 11b, and the negative electrode plate 11c of the battery part 11 has a size different from each other, the case 12 is manufactured while having some spare when forming the battery part space 12b of the case 12. As a result, at the time of the vacuum adsorption of the case 12, impact is applied to the battery part 11 due to a gap 15 between the case 12 and the battery part 11, such that the positive electrode plate 11a and the negative electrode plate 11c may be damaged due to the impact. Particularly, when a portion of the plates is separated by the impact to thereby float in the case 12, the pouched cell 10 may be damaged and performance may be degraded.
Therefore, a development of a battery cell for preventing the damage of the battery part 11 by minimizing the impact on the case 12 and the battery part 11 at the time of the vacuum adsorption of the case 12 has been demanded.